1. Field of the Invention
This invention relates to ultrasonic imaging and, more particularly, to structures and methods forming electrical assemblies for acoustic sensors.
2. Background Art
In many ultrasound imaging systems, transducer element signals are generated in a hand-held probe unit and sent to a system console through a multi-channel cable system. In some of these systems a probe may utilize a relatively small array of 128 or 256 transducer elements with each element connected to the console via the cable system. Real time 3D ultrasound imaging systems may use larger 2D arrays of transducers. There are applications in which it is desirable for large ultrasound arrays to contain thousands or tens of thousands of transducer elements. With such a large number of elements, it becomes difficult to route individual connections between elements in a hand-held probe unit and electronics in the system console.
In medical imaging applications, this problem has been addressed, in part, by placing a limited portion of the processing circuitry in the probe unit instead of in the console. Some designs form the large array of transducer elements in subarrays, each perhaps containing 10 to 40 elements, and each subarray has a dedicated circuit unit providing part of the beamforming function. Each subarray circuit unit can transfer the signals from all of the transducer elements in the subarray to a single channel or wire, e.g., by analog beam formation, so that the signals for all of the elements in the subarray can be transferred via a single cable lead to the processing circuitry in the console. In this way thousands of signals can be carried on a more limited number of lines, resulting in a manageable cable size.
With continued increases in the size of transducer arrays in an ultrasound system, it is desirable to place even more processing electronics in the assembly housing. However, in medical applications requiring relatively small, light-weight hand-held probe units, it becomes more of a challenge to provide systems with higher resolution capability while meeting size and weight constraints.
Movement of more circuit functions into a hand-held probe unit can reduce the wire count at the interface between the probe unit and the cable assembly. This requires an extensive number of additional connections and routings among transducer elements and circuit elements which may be placed on multiple circuit boards. With the transducer array formed along a major plane, a large number of flexible circuit boards are each positioned with a major surface thereof in an orthogonal orientation relative to the major plane along which the transducer array is formed. In such a configuration, a transducer array having, for example, 64 rows of elements, can require connection with 64 individual flex circuits. Additional electronic components providing circuit functions such as pulse generation and beamforming may be connected to each of the individual flex circuits, resulting in a relatively large and complex assembly. Thus while increasing the sizes of image arrays, e.g., for purposes of increasing image resolution or field, there is, simultaneously, a need to further reduce the size, complexity and number of components in the electrical connection structure.